A combined kinetico-mechanistic and computational study on the competitive formation of seven- versus five-membered platinacycles; the relevance of spectator halide ligands

作者：Aullon Gabriel; Crespo Margarita^*; Font Bardia Merce; Jover Jesus; Martinez Manuel; Pike Jack

来源：Dalton Transactions, 2015, 44(41): 17968-17979.

DOI：10.1039/c5dt02657a

The metalation reactions between [Pt-2(4-MeC6H4)(4)(mu-SEt2)(2)] and 2-X, 6-FC6H3CH=NCH2CH2NMe2 (X = Br, Cl) have been studied. In all cases, seven-membered platinacycles are formed in a process that involves an initial reductive elimination from cyclometallated Pt-IV intermediate compounds, [PtX(4-CH3C6H4)(2)(ArCH=NCH2CH2NMe2)] (X = Br, Cl), followed by isomerization of the resulting Pt-II complexes and a final cyclometallation step. For the process with X = Br, the final seven-membered platinacycle and two intermediates, isolated under the conditions implemented from parallel kinetic studies, have been characterized by XRD. Contrary to previous results for the parent non-fluorinated imine 2-BrC6H4CH=NCH2CH2NMe2 the presence of a fluoro substituent prevents the formation of the more stable five-membered platinacycle. Temperature and pressure dependent kinetico-mechanistic and DFT studies indicate that the final cyclometallation step is strongly influenced by the nature of the spectator halido ligand, the overall reaction being much faster for X = Cl. The same DFT study conducted on the previously studied systems with imine 2-BrC6H4CH=NCH2CH2NMe2 indicates that, when possible, five-membered platinacycles are kinetically preferred for X = Br, while the presence of Cl as a spectator halido ligand leads to a preferential faster formation of seven-membered analogues.

• 出版日期2015